How to allow only the administrator to update a web application ?

During an update of a web application (launching the Windows installer or updating the debian package), the installer performs the following operations:

  - save configurations (already done by installers normally)

  - copy of new sources (already done by installers)

  - modification of entry points to redirect to the application "setup"

my question is: how to check if a user is an administrator if ok we launch the update from the webGUI your suggestions!